The fiction part of science-fiction gets a real workout in “Snowpiercer,” the opening night gala feature of the 2014 LA Film Festival that screened June 11. Set almost entirely inside a train that’s circling a frozen Earth (yes, the track, somehow, even crosses oceans), Bong Joon Ho’s political parable requires some Diesel-powered suspension of disbelief, even if one’s able to view the whole thing as a social metaphor.

If you can do that, though, you’re in for quite a ride. Starring Chris Evans, Tilda Swinton, Jamie Bell, Octavia Spencer, John Hurt, Ed Harris and Song Kang Ho, the film, based on a French comic book, is a crazy, blood- and action-soaked piece of bravura filmmaking.

We expect nothing less from Bong, the South Korean genre master who handily out-Godzillad the giant monster movie with “The Host” and exhumed everything that’s great about the Hitchcock thriller in “Mother.” His first English-language film is miles ahead of any previous efforts to bring Seoul to Hollywood, and it operates on a level that Roland Emmerich could never imagine. Nevertheless, it won’t be mistaken for a total success.

The ice age’s survivors have been protected on the train for 17 years, but have also been ruthlessly segregated by class. The poor live in squalor at the rear, the lucky ones in decadent indulgence up toward the perpetual motion engine, with all of their support systems on cars in between. Evans, who is more recently swooned over as the clean-cut Captain America, was barely recognizable in rags and stubble as he led an underclass rebellion in the film that grows increasingly surreal and deadly, as his grimy forces move forward.

It’s a hoot — for a movie that starts off gloomy and grows increasingly depressing, anyway.

Enjoy it or not, there’s always something fascinating to take in from this looped-out loop of a movie — or at least to make you stop wondering who’s maintaining the tracks on this lifeless, storm-battered world for awhile.